Primary exercises
- Manually created factor.
In a study participants were asked whether their sport activity is
none, oncePerWeek, severalPerWeek
or daily.
Build a proper factor for the responses below and store it in a variable
w.
Print the factor.
Write the code to count the numbers of occurrences of each level and
print the counts.
severalPerWeek, none, none, oncePerWeek, oncePerWeek, oncePerWeek, oncePerWeek, ?, none, none
v <- c( "severalPerWeek", "none", "none", "oncePerWeek", "oncePerWeek", "oncePerWeek", "oncePerWeek", NA, "none", "none" )
w <- factor( v, levels = c( "none", "oncePerWeek", "severalPerWeek", "daily" ) )
w
[1] severalPerWeek none none oncePerWeek oncePerWeek oncePerWeek
[7] oncePerWeek <NA> none none
Levels: none oncePerWeek severalPerWeek daily
fct_count( w )
# A tibble: 5 × 2
f n
<fct> <int>
1 none 4
2 oncePerWeek 4
3 severalPerWeek 1
4 daily 0
5 <NA> 1
- A factor with a random content.
Read help about the function sample.
Then study and try the following lines of code to understand the
results.
Next, understand why an error is generated and use replace
argument to generate a vector with 100 samples.
Store this vector in a variable v and build a factor
w from it.
Finally, count the numbers of occurrences of each level in
w.
Ensure, that levels are in order provided in the variable
lvl.
lvs <- c( "none", "oncePerWeek", "severalPerWeek", "daily" )
sample( lvs, 3 )
[1] "oncePerWeek" "daily" "none"
sample( lvs, 3 )
[1] "severalPerWeek" "daily" "none"
sample( lvs, 3 )
[1] "daily" "none" "oncePerWeek"
sample( lvs, 100 )
Error in sample.int(length(x), size, replace, prob): cannot take a sample larger than the population when 'replace = FALSE'
v <- sample( lvs, 100, replace = TRUE )
w <- factor( v, levels = lvs )
w
[1] oncePerWeek oncePerWeek daily oncePerWeek daily daily
[7] daily severalPerWeek severalPerWeek none daily severalPerWeek
[13] daily oncePerWeek none oncePerWeek oncePerWeek none
[19] daily daily daily daily daily daily
[25] oncePerWeek oncePerWeek severalPerWeek daily severalPerWeek daily
[31] oncePerWeek severalPerWeek oncePerWeek none oncePerWeek severalPerWeek
[37] none severalPerWeek oncePerWeek daily daily none
[43] severalPerWeek none daily severalPerWeek daily none
[49] oncePerWeek none none oncePerWeek severalPerWeek daily
[55] daily daily severalPerWeek oncePerWeek daily daily
[61] oncePerWeek oncePerWeek oncePerWeek oncePerWeek oncePerWeek none
[67] severalPerWeek none severalPerWeek severalPerWeek oncePerWeek none
[73] daily none severalPerWeek severalPerWeek oncePerWeek oncePerWeek
[79] severalPerWeek none severalPerWeek none severalPerWeek none
[85] oncePerWeek oncePerWeek severalPerWeek daily daily oncePerWeek
[91] oncePerWeek none none severalPerWeek daily none
[97] severalPerWeek severalPerWeek severalPerWeek daily
Levels: none oncePerWeek severalPerWeek daily
fct_count( w )
# A tibble: 4 × 2
f n
<fct> <int>
1 none 20
2 oncePerWeek 27
3 severalPerWeek 25
4 daily 28
- Reordering factor levels.
When a factor is shown on an axis of a plot, the order is given by its
levels.
The factor w from the previous exercise will be then shown
in this order: none, oncePerWeek,
severalPerWeek, daily.
But for a picture in a manuscript the following order might be needed:
daily, severalPerWeek,
oncePerWeek, none.
Apply to w one of the fct_ functions from the
tidyverse library to produce a factor w2 with
the requested order.
Show the levels of w2.
Again show the number of elements of each level in w2 and
compare it with the table of the previous exercise.
w2 <- fct_relevel( w, c( "daily", "severalPerWeek", "oncePerWeek", "none" ) )
levels( w2 )
[1] "daily" "severalPerWeek" "oncePerWeek" "none"
fct_count( w2 )
# A tibble: 4 × 2
f n
<fct> <int>
1 daily 28
2 severalPerWeek 25
3 oncePerWeek 27
4 none 20